He was also named as a suspect last year in the 1970s killings of three women in Rochester, New York which took place in almost identical circumstances. One of those women even bore the same name - Carmen Colon - as a California victim.

Naso was a native of Rochester and travelled regularly between the two US coasts.

Marin County District Attorney Ed Berberian told Reuters he believes Naso killed at least 10 women over several decades but that authorities "were not able to marshal enough evidence" to present charges in all 10 of those cases.

Naso defended himself in the California trial and his arguments at times seemed confused. On Friday he claimed in court that DNA evidence implicating him had been planted on two of the murdered women and that he was no monster.

"I have sympathy, remorse for anybody who dies and the people they leave behind," he said. "But I'm not guilty of these crimes."

But Marin County Judge Andrew Sweet insisted Naso was a "ruthless, pathological predator", saying the evidence had clearly established he was an "evil and disturbed man".

"Your being in the world has made this a worse place, and for your atrocious crimes you are going to be sentenced to the ultimate punishment," he said.

Naso was finally connected to the murders in 2010 after probation officers visiting his Reno home discovered hundreds of photographs of naked women in unnatural positions. They appeared unconscious or dead.

They also found ammunition, erotically dressed mannequins, handcuffs, and journals detailing numerous rapes of women and underage girls dating back to the 1950s.

One key item of evidence turned up by investigators was the "List of 10", a handwritten numbered roster detailing nine locations in California and one in Florida, where authorities believe Naso dumped his victims' bodies.

Analysts said that despite the death sentence, Naso was unlikely to ever be executed as he could well die of natural causes first.

Now stooped and balding, Naso will be the oldest convict to arrive on Death Row in California since the state resumed executions in 1977 after a five-year-hiatus.

There are 745 inmates already on California's Death Row, and executions have been on hold since 2006, when a federal judge halted them saying the three-injection method risked inflicting too much pain and suffering.

Richard Dieter, executive director of the Death Penalty Information Center called Naso's punishment "purely a symbolic gesture with very little chance of being carried out".